Gas blanket controllers are used to sense pressure in a tank and control the flow of blanket gas to the tank. In one prior art design, gas pressure is provided to one side of a diaphragm to which is attached a rod. The rod is biased by a spring and connects directly to a valve to control flow of blanket gas into the tank. This arrangement is somewhat cumbersome and the inventor considers it hard to adjust to a set pressure. A simpler, more dependable and more accurate design is desirable.